Glaucoma is a disease characterized by high intraocular pressure (IOP) sufficient to cause either temporary or permanent impairment of vision. The rise in IOP might be due to:                Increased rate of aqueous formation        Decreased rate of out flow        Raised pressure in the draining episcleral veins.        
An obstruction to the circulation of the aqueous at the pupil or to its drainage through the angle of the anterior chamber causes glaucoma. The normal IOP of an individual ranges up to 20 mm Hg and can rise up to 60 to 70 mm of Hg in glaucoma patients. Raised IOP of this magnitude can result in loss of vision by causing damage to retinal nerve fibers. Optic nerve axons of the eyeball become compressed at the optic disc due to elevated IOP. This compression probably blocks the axonal flow of cytoplasm from the neuronal cell bodies in the retina to the extended optic nerve fibers entering the brain. It results in lack of nutrition of fibers and ultimately causes death of the neurons. Compression of retinal artery may increase the neuronal damage due to reduction in retinal nutrition.
Glaucoma is Generally Classified as
                Primary        Developmental        Secondary        
The commonest form of glaucoma is primary glaucoma; it can be:
Open Angle Glaucoma:
Angle of the anterior chamber is always open, at all stages of disease, and aqueous has access to the outflow channels at all times. There is increased resistance to outflow in the corneoscleral meshwork. IOP may be raised or elevated.
Angle Closure Glaucoma:
No abnormal resistance to outflow in the corneoscleral meshwork is observed. The sole cause of elevated tension is closure of the angle. The iris obstructs the access of aqueous humor to the outflow channels.
Magnitude of the Disease
Glaucoma is the third major cause of avoidable blindness. The global estimate of blindness is over 44 million with glaucoma accounting for more than 15% of the blind patients worldwide (2). Worldwide approximately two-thirds of all blind or visually impaired people are women (3). India has a high burden of blind (23.5%) in the world and 13% of the global blindness due to glaucoma is in India. Many population-based surveys carried out in the west and in Asia have shown that glaucoma remains undetected in nearly 50% of the cases and hence glaucoma related blindness and disability is often underestimated (4-5).
Prompt and effective management of glaucoma is necessary to reduce the incidence of cases of bilateral blindness due to progressive glaucoma. Biological revolution in medicine has provided new avenues for therapeutic intervention. Newer and innovative treatment strategies are being considered for the control of raised intraocular pressure (TOP) by the use of synthetic and herbal drugs in glaucoma.
Presently Available Glaucoma Therapy
The primary goal in the management of glaucoma is to lower IOP below 20 mm Hg in the patients with mild changes in the optic disc and below 15 mm Hg in the patients with more severe changes. Surgical intervention aiming at increasing the aqueous humor outflow is undertaken when IOP remains uncontrolled even with multiple drug therapy.
The following groups/drugs are widely used in the treatment of glaucoma:
Group of DrugsFormulationsTOPICAL DRUGSCholinergic agonistsPilocarpine, carbechol, physostigmineAdrenergic agonistsForskolin, isoproterenol, salbutamol,epinephrineAdrenergic antagonistsTimolol, betaxolol, atenololProstaglandin analoguesLatanoprostCarbonic anhydraseTrifluoromethazolmide, aminozolamideinhibitorsSYSTEMIC DRUGSCarbonic anhydraseAcetazolamide, methazolamide,inhibitordichlorphenamideHyper- osmotic agentsGlycerol, mannitolMiscellaneousCannabinoids, prostaglandins, ACEinhibitors, melatonin, calciumchannel blockers, haloperidol.Drawbacks of the Presently Available Treatment
Synthetic drugs are currently available for the control of intraocular pressure (IOP) but have the drawbacks of being toxic, expensive and often have to be administered multiple times a day resulting in poor patient compliance. Thus, an inexpensive drug with potent ocular hypotensive effect and devoid of side effects with low frequency of application is desirable and its identification will be major achievement for human welfare. Medicinal plant based formulations are being used since long for a variety of diseases. Pilocarpine is one example of antiglaucoma drug of plant origin. A variety of substances of plant origin are known to have antichlolonergic and diuretic activity. Such drugs might be useful antiglaucoma drugs.
Following are the adverse reactions observed for synthetic drugs:
Adverse reactionsPharmaceutical agentsOcularSystemicCholinergic agonistStinging, irritationHeadache, painPilocarpineCiliary spasms (myopia)SweatingMiosis (vision)Vomiting/diarrheaPupillary blockSalivation, BradycardiaRetinal detachmentArrhythmiaDyspneaAdrenergic agonistStinging, burningIncreased bloodEpinephrineMydriasisPressureAllergic sensitivityIncreased heart ratePigment depositsSevere headachesCystoid macular edemaAnxietyIncreased intraocular pressure (IOP)Alpha-2 agonistsAllergic sensitivityGastrointestinalClonidineMinimal mydriasisDiscomfortLid retractionTaste abnormalitiesConjunctival vasoconstrictionHeadacheStinging, burningFatigue/drowsinessForeign body sensationOral drynessHyperemiaConjunctival folliclesTopical beta-blockersStinging, burningDyspneaTimololSuperficial punctate keratitisBronchiole constrictionBetaxololAllergic sensitivityDecreased heart rateDecreased corneal sensitivityArrhythmiasUveitis 4Decreased bloodPressureDepression, confusionGastrointestinalDiscomfortOral carbonicNoneMalaiseanhydrase inhibitorsDepression, confusionAcetazolamideMetallic tasteAnorexiaDiarrheaTopical carbonicStinging/burningAltered tasteanhydrase inhibitorsAllergic sensitivityDorzolamideBlurred visionSuperficial punctatekeratitisCorneal edemaProstaglandin analogsBlurred vision, Stinging, burning,HeadachesLatanoprostHyperemiaUpper respiratory tractForeign body sensationSymptomsItching.